Electric contacting element



Patented July 15, 1941 ELECTRIC CONTACTING ELEMENT Franz R. Hensel,Indianapolis, Ind., assignor to P. R. Mallory & 00., Inc.,Indianapolis,lnd., a corporation of Delaware No Drawing. Originalapplication June 28, 1937, Serial No. 150,756. Divided and this application January 16, 1940, SerialNo. 314,052 r 1 Claim.

This invention relates to electric contacting elements of the typeincluding contactor contacts and pressure exerting welding electrodes.

vcompositions'can be chosen'so. as to provide the most suitableproperties for the purposes:

r Per cent This application is a division of prior-filed co- A. Chromium0.5 pendin application Serial No. 150,756, filed June 5 Cadmium -1- 1.2528, 1937. Silicon 1.00

An object of the invention is to improve the Copper Balance. strength,hardness and temperature-resistant B. Chromium 0.5 properties ofcontacting elements of the type dis- Cadmium 1.00 closed. Silicon .0.15

Further objectsare to prevent oxidation of Copper Balance .the elementsboth during and after formation C. Chromium 0.5 thereof. v Cadmium 1.00.

A specific object is to produce a contacting Silicon -0.25 element suchas a welding electrode or a con Copper Balance. tact where certaindesired electrical'and heat D; Chromium 0.50 conductivity coupled withhigh strength is re- Cadmium 1.25 quired in a non-ferrous material.Silicon 2.5

Other objects of the invention will be apparent Copper Balance from thefollowing description taken in connec- I tion with th appended claim Ihave found that the characteristics of my The present inventioncomprises the combinaalloy are n t C a d materially Small q tion ofelements, methods of .manufacture, and tities f such elements e added, sve ,ma the product thereof brought out "and exemplified esi i m, e,aluminum, titanium, in the disclosure hereinafter set forth, the-scopecomum, an a ese an a metal of the iron of the invention being indicatedin the appended group, Such as Q cobalt llickel- In ome claim uses, theaddition of silver up to 1% will mate- The invention contemplates theprovision of rially impr v e 9, 3-

a contacting element of copper, chromium, sili- I11 Producing the alloyt e p sent invencon and cadmium. This alloy has a number of 151011, P Ofthe eadmium. Chromium and S con desirable properties which render itsuitable for s Ordinarily 10st thliough at on and Volatilicertainspecified useswhe're high strength a p. pzation during melting, pouringand other hantain' desired electrical and. heat conductivity, d n It snecessary; therefore, to introduce high resistance to corrosion,- highhardness, oran excess of these elements intO t e elt in high areSnufling ability may be required order'that the finished alloy will havethe com- The completedcopper-chromium-silicon-cad- P n given above.- tmium alloy, to have the most desirable char- The additives y beintroduced into the acteristics, should contain the component ingre-,copper'in a Variety O y -ta en to clients in the following ranges ofproportions; avoid unnecessary oxidation and volatilization' r I p t 0of oxidizable ingredients. According to one Cadmium 0.1 to 3.0 h d acopp r-cadmium alloy is first made by Chromium 0.1 l to 2.5 u ualalloying methods- The-chromium and sili- 'Silicon 0.05 to 5.0 0011 m ythen be ad ed in finely divided form, Copper Balance Preferably Comb nedWith copper powder in the form of a briquette, and intimately mixedthere- The following fourspecific compositions'are with. The chromiumand silicon may also be listed as examples of the above composition, theadded combined with copper to form a hardener properties varyingsomewhat depending upon the alloy containing 10 to 25% of theseingredients.

specific proportions of ingredients used. It will This hardener may beprepared by melting tobe apparent that for any specific application thegether copper, chromium and silicon under a protective atmosphere. Thecadmium is preferably added to the melt before the chromium in order toavoid chromium losses.

In many cases it will be found preferable to make a master alloy havingrelatively high percentages of chromium, cadmium, silicon, alloyed withcopper. This alloy may then be diluted with copper to form lowerpercentage alloys.

The cadmium used in producing the present alloy is utilized in two ways.Part of it is used up as a deoxidizer and part of it remains as aningredient in the finished alloy. In order to have 1% cadmium inthefinished alloy, for example, it is necessary to introduce about 1.20%cadmium into the original melt. About half of the excess cadmium isconsumed as a deoxidizer, the cadmium being converted to cadmium oxideand separating as a slag. The rest of the excess is volatilized due tothe low boiling point of the cadmium.

Some of the chromium andsilicon are likewise oxidized during thealloying process and accumulates on the top of the melt as part of theslag. In order to obtain 0.5% chromium in the finished alloy it isnecessaryto. add approximately 1.0% chromium to the melt.

In the further treatment of the alloy after solidification it may befirst heated to a temperature of 600 C. to 1050 C. and preferably above700 C. for a short time, such as from to 30 minutes. After the metal hasreached the desired temperature, it may be cooled quickly from the hightemperature (quenched). The next step is preferably to heat treat thequenched alloy at a temperature of 350 C. to 600 C. for a period of timefrom 10 minutes to 30 hours, depending on the temperature, thepercentage of hardener used, and the results desired.

The alloy may then be cold worked toobtain a cold reduction ofapproximately and further cold reduction, up to 50% or more, may beapplied to further increase the hardness. It has been found that theconductivity will not be appreciably decreased by these furtherreductions.

For maximum hardness and conductivity, however, it is preferable toapply a series of cold reductions alternated with relatively lowtemperature heat treatment, preferably within the range 400 C. to 500 C.The number of cold workings with intermediate heat treatments may varywith the properties desired in the finished product.

Instead of cold working the alloys they may be hot forged according tousual methods and it will be found that the resulting hot-forged productwill also have a hardness greater than the alloys of the prior art.

The finished alloy has marked heat-resistant properties whereby it isable to maintain its hardness at temperatures of 400 C. to 475 C. orhigher. Thus, where the alloy has been age-hardened it will be suitablefor applications where a combination of high'hardness, strength and heatresistance are required.

The alloy is highly fluid in the may be readily cast.

Since the cadmium acts as a strong deoxidizer it is not necessary to addother deoxidizers commonly used, such as aluminum or magnesium, for thispurpose.

The presence of the cadmium likewise tends to prevent excessive surfaceoxidation in the finished, solidified alloy and is particularlyadvantag'eous where they are heated to high temperatures. The surfaceoxidation in copper-chromi-. urn-silicon alloys is quite serious sincethe oxygen penetrates along the grain boundaries and tends to make thealloy brittle. In the alloy the chromium and silicon are protected bythe cadliquid state aid mium, which will oxidize in preference to theseelements.

The contacting elements have improved arcsnuffing properties, due to thepresence of the cadmium.

This alloy is characterized by small grain size.Copper-chromium-silic'on materials must be heated to above 900 C. beforequenching in water. That elevated temperature, however, is normally veryconducive to grain growth, the size of the grains usually depending onthe length of time the material is held at the elevated temperature.grain size appears to be considerably reduced from that found in othercopper-chromium-silicon alloys.

The alloy can be cast in chill molds or sand cast with ease and with lowcadmium content can be mechanically worked in the hot or cold state withthe same ease. It is likewise well adapted to machining.

The hardness and electrical conductivity of the finished material willvary considerably with the proportions of the ingredients used. Ingeneral the alloys having the higher proportions of silicon will behigher in strength and hardness but lower in electrical conductivity.

While the present invention, as to its objects and advantages, has beendescribed herein, as carried out in specific embodiments thereof, it isnot desired to be limited thereby, but it is intended to cover theinvention broadly within the spirit and scope of the appended claim.

What is claimed is:

An electric contacting element of the type comprising contactor contactsand pressure exerting electrodes, said element being composed of 0.1 to3.0% cadmium, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon and the balancesubstantially all 7 copper.

FRANZ R. HENSEL.

With the alloy containing cadmium the I

